1. Field of the Invention
The present invention relates to a monitor information transmitting/receiving apparatus in each cable landing station in a submarine cable system in which a plurality of cable landing stations are arranged in the form of a ring and, more particularly, to a transmitting/receiving apparatus for transmitting/receiving monitor information about the self-station and a remote station in a submarine cable system.
2. Description of the Prior Art
As the demand for international lines grows, the line quality of the internal lines is considered more important. When a line fault occurs, a terminal apparatus in the cable landing station accommodating the corresponding line transmits many warnings to remote stations. In order to maintain high internal communication quality, each station in the system must monitor the states of each line and station in the system by obtaining monitor information about remote stations. In the submarine cable system, communication is often performed between two or three cable landing stations. In this system, it is relatively easy for a given cable landing station to obtain monitor information such as fault information about remote stations.
In some submarine cable system, a plurality of cable landing stations are arranged in the form of a ring. In such system, when a given station is to obtain monitor information about each station, the given station must also obtain monitor information from stations to which the given station is not directly line-connected. In a communication system constituted by terrestrial stations, a LAN for transmission/reception of monitor information can be easily installed in addition to lines for communication. In a submarine cable system, however, it is difficult to perform such operation, and hence monitor information must be transmitted/received by using the lines of the submarine cables for communication.
As described above, in a submarine cable system in which a plurality of cable landing stations are arranged in the form of a ring, each station must obtain monitor information about remote stations by using limited lines. In addition, as described above, to maintain high internal communication quality, each station in the system must accurately obtain monitor information about remote stations.
For example, a scheme of transmitting/receiving monitor information between two cable landing stations in a submarine cable system is disclosed in Japanese Unexamined Patent Publication No. 4-122127.